I think if you want to simply beat the game, and be the best that the game can offer, the default levelling system suits, because, if your not bothered about how your character looks, or act's then repeatedly doing actions over and over again to level up won't matter.
I've never tried efficient levelling on any of my other characters, and don't intend to. What's the point? Surely efficient levelling only comes into play if you have major's like speechcraft and mercantile? My other characters have always been strong enough to tackle the higher level creatures. It's not like your levelling at a much slower rate than the enemies, your increasing at the same. A good restoration spell mixed in with some paralyzeing and shock, plus a few strikes with a sword surely shoulden't be that hard, or are people not wanting a challenge? People bleet on about roleplaying over and over again, but what's the point in playing the game, if your actually not playing it realistically, your going to die sometimes, it's a game, it doesent have a purpose if it's not challenging does it.
I fully understand using other levelling mods when roleplaying, because of how the default levelling system works, you can't effectively roleplay well, without looking daft, so I do understand this. I do think it depends what you want to roleplay though. My only roleplaying character, an alchemist, is highly skilled in Alchemy, but nothing in anything else, using the default levelling system. This is realistic though isn't it? An alchemist is hardly going to be the strongest with a blade.
But, im going have to check out this realistic levelling mod, but I need some more roleplaying ideas!